It is often difficult to provide reliable couplings between a push-pull wire and the deflectable distal end portion of a deflectable catheter. Welding or soldering the push-pull wire to a marker band in the deflectable distal end portion can anneal a portion of the wire adjacent to the weld. The annealed portion of the wire is sometimes weakened relative to the rest of the push-pull wire. When the push-pull wire experiences the stress of repeated pushing and pulling from an actuator the wire may fracture in the annealed region. Additionally, the marker band extends remotely from the push-pull wire around the catheter body. Pushing and pulling forces can tear the pull ring apart through shearing forces thereby freeing the push-pull wire to undesirably move within the catheter.
Often, the deflectable distal end portion of the catheter is in a deflected position within a curved vessel when the push-pull wire fractures. If pushing forces are applied to the push-pull wire after fracture, the fractured end of the push-pull wire may puncture the sidewall of the deflected catheter. Further, if the catheter is in a substantially non-deflected position and pushing forces are applied to deflect the catheter, the fractured end of the push-pull wire may puncture the distal end of the catheter.
Moreover, fracturing the wire prevents transmission of pushing and pulling forces to the deflectable distal end portion. Failure of the push-pull wire can complicate a medical procedure. For instance, the catheter must be withdrawn through curving vasculature, possibly in a deflected position created prior to fracture of the push-pull wire. The deflected catheter can snag within the vasculature and complicate the extraction. Further, the catheter must be exchanged with another deflectable catheter and the vasculature traversed again to complete the medical procedure.
In other examples, the push-pull wire is retained within a deflectable distal end portion by adhesives and the like. Assembling a catheter with an adhered push-pull wire is complex and requires hollowing out a portion of the catheter and injecting the adhesive into the hollowed out portion of the catheter to couple the push-pull wire with the deflectable distal end portion. In still other examples, the push-pull wire is adhered to the catheter with a hardened distal end portion. The push-pull wire is potted (i.e., covered on its distal and side surfaces) with the adhesive that forms the distal end portion. Compressive stresses from the push-pull wire can dislodge the distal end portion and cause failure of the catheter. Additionally, the adhesives used to form the distal end portion create a hard structure that has little or no deformability and can therefore be traumatic when engaged against the soft tissues of vasculature and organs.
What is needed is a push-pull wire anchor that overcomes the shortcomings of previous designs. What is further needed is a push-pull wire anchor that substantially prevents fracture of the push-pull wire and puncturing of a catheter by a fractured push-pull wire.